Apparatus for providing large amounts of gas to a fermentation broth

ABSTRACT

A system for delivering air to an aqueous liquid for aerobic fermentation of the aqueous liquid includes a vessel having a length to diameter ratio of less than 2:1, an aeration system including at least one sparge tube having a pore size of less than 5 microns and a porosity of greater than 50 percent in fluid communication with an interior of the vessel, at least one blower configured to deliver air at a pressure of less than 15 psig to the at least one sparge tube, and a heat exchanger in fluid communication between the at least one blower and the at least one sparge tube that cools the air to below 100° F. (37.8° C.) prior to entering the at least one sparge tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. § 120 of U.S. patentapplication Ser. No. 15/112,909, titled AN APPARATUS FOR PROVIDING LARGEAMOUNTS OF GAS TO A FERMENTATION BROTH, filed Jul. 20, 2016, which is aU.S. National Phase Application under 35 U.S.C. § 371 of International(PCT) Patent Application Serial No. PCT/US2016/041038, filed Jul. 6,2016, which claims priority under 35 U.S.C. § 119(e) to U.S. ProvisionalPatent Application Ser. No. 62/189,316 filed Jul. 7, 2015, thedisclosures of which are hereby incorporated by reference in theirentireties.

BACKGROUND Technical Field

The technical field relates generally to methods and systems forproducing a fermentation product from a cellulosic or lignocellulosicbiomass.

Background Discussion

Lignocellulosic biomass, such as agricultural residues, woody biomass,municipal waste, oilseeds/cakes, and seaweeds function as renewablefeedstock that may be used for manufacturing bioproducts, such asbiofuels and biochemicals. Many of these biomass materials areattractive in that they are abundant, renewable, domestically produced,and may not compete with food industry uses. Currently, many of thesematerials are used as animal feed, biocompost material, burned in acogeneration facility or landfilled. Lignocellulosic biomass isrecalcitrant to degradation as the plant cell walls have a structurethat is rigid and compact. Saccharides from renewable biomass sourcescould become the basis of chemical and fuels industries by replacing,supplementing or substituting petroleum and other fossil feedstocks.

Fermentable sugar solutions may be produced from the polysaccharidecomponents of the feedstock, such as cellulose and hemicelluloses. Inorder to produce sugar from lignocellulosic feedstocks, it is firstnecessary to break them down into their composite sugar molecules. Thiscan be accomplished by physical and/or chemical pretreatment. Examplesof chemical pretreatment are acid pretreatment (see U.S. Pat. No.4,461,648) or alkali pretreatment, such as Ammonia Fiber Explosion(AFEX) pretreatment. Acid pretreatment hydrolyzes most of thehemicellulose, but there is little conversion of the cellulose toglucose. On the other hand, alkali pretreatment methods may or may nothydrolyze hemicellulose, although in either case the base reacts withacidic groups present on the hemicellulose to open up the surface of thesubstrate. After pretreatment with acid or alkali, the cellulose maythen be hydrolyzed to glucose by cellulase enzymes or by furtherchemical treatment. Glucose can then be fermented to fuels including,but not limited to, ethanol, butanol, or other chemicals, examples ofwhich include sugar alcohols and organic acids.

SUMMARY

Aspects and embodiments are directed to systems and methods forfermenting and to delivery of gases, such as air to fermentation broths.For example, systems and methods are described that provide largeamounts of a gas, such as air, that can be used for aerobicfermentation. The gas, such as air, can be provided at a fraction of thecost of high pressure compressed gas, such as those routinely used invarious fermentations. For example, relatively low pressure air, e.g.,less than 25 psig, can be provided for the production of proteins, suchas enzymes, e.g., cellulases. In addition to providing a gas, such asair, at a fraction of the cost of high pressure gas systems, the systemsand methods described herein have lower capital costs and lowermaintenance in comparison to typical high pressure systems.

In accordance with one or more embodiments, a system for delivering agas to an aqueous liquid, such as a system for aerobic fermentation ofan aqueous liquid, is provided. The system may comprise: a vessel, atleast one sparge tube in fluid communication with an interior of thevessel, and at least one blower configured to deliver a gas to the atleast one sparge tube. According to some embodiments, the at least onesparge tube is constructed from a porous metal. According to at leastone embodiment, the at least one sparge tube is positioned in a lowerportion of the vessel.

In accordance with certain embodiments, the vessel has an aspect ratioof 2:1.

According to another embodiment, the system further comprises at leastone filter configured to filter air delivered from the at least oneblower to the at least one sparge tube. According to another embodiment,the system further comprises a heat exchanger having an inlet in fluidcommunication with an outlet of the blower and an outlet in fluidcommunication with the at least one filter. According to yet anotherembodiment, the system further comprises flexible conduit materialcoupled to the at least one filter and the heat exchanger. According toanother embodiment, the system includes a plurality of filterspositioned at equidistant positions around a perimeter of the vessel.

According to at least one embodiment, the system further comprises atleast one condenser in communication with an interior of the vessel andis configured to condense sparge bubbles.

According to another embodiment, the system further comprises a mixingsystem positioned within the interior of the vessel.

In accordance with certain embodiments, the at least one blower isconfigured to deliver air at a pressure of 20 psi.

In accordance with one or more embodiments, a system for providing gasto a fermentation process is provided. The system comprises: afermentation broth and at least one gas blower in fluid communicationwith the fermentation broth.

According to another embodiment, the at least one gas blower includes agas production portion configured to generate gas and a gas deliveryportion configured to provide the gas to the fermentation broth.

Still other aspects, embodiments, and advantages of these exampleaspects and embodiments, are discussed in detail below. Moreover, it isto be understood that both the foregoing information and the followingdetailed description are merely illustrative examples of various aspectsand embodiments, and are intended to provide an overview or frameworkfor understanding the nature and character of the claimed aspects andembodiments. Embodiments disclosed herein may be combined with otherembodiments, and references to “an embodiment,” “an example,” “someembodiments,” “some examples,” “an alternate embodiment,” “variousembodiments,” “one embodiment,” “at least one embodiment,” “this andother embodiments,” “certain embodiments,” or the like are notnecessarily mutually exclusive and are intended to indicate that aparticular feature, structure, or characteristic described may beincluded in at least one embodiment. The appearances of such termsherein are not necessarily all referring to the same embodiment.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects of at least one embodiment are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide an illustration anda further understanding of the various aspects and embodiments, and areincorporated in and constitute a part of this specification, but are notintended as a definition of the limits of any particular embodiment. Thedrawings, together with the remainder of the specification, serve toexplain principles and operations of the described and claimed aspectsand embodiments. In the figures, each identical or nearly identicalcomponent that is illustrated in various figures is represented by alike numeral. For purposes of clarity, not every component may belabeled in every figure. In the figures:

FIG. 1 is a process flow diagram illustrating conversion of a biomassfeedstock to one or more products in accordance with one or more aspectsof the disclosure;

FIG. 2 is a schematic representation of the conversion of sugar intocarbon dioxide gas and a sugar alcohol in accordance with one or moreaspects of the disclosure;

FIG. 3 is a perspective view of a fermentation system in accordance withone or more aspects of the disclosure;

FIG. 4 is a perspective view of a blower skid in accordance with one ormore aspects of the disclosure;

FIG. 5 is a side view of the blower skid featured in FIG. 4;

FIG. 6 is a top view of the blower skid featured in FIG. 4;

FIG. 7 is a schematic of the fermentation system featured in FIG. 3;

FIG. 8 is a perspective view of an inlet filtration apparatus inaccordance with one or more aspects of the disclosure;

FIG. 9 is another perspective view of the inlet filtration apparatusfeatured in FIG. 8;

FIG. 10A is a perspective view of a condenser in accordance with one ormore aspects of the disclosure;

FIG. 10B is a side view of the condenser featured in FIG. 10A;

FIG. 11 is a perspective view of an outlet filtration assembly inaccordance with one or more aspects of the disclosure;

FIG. 12 a top view of the outlet filtration assembly featured in FIG.11;

FIG. 13A is a side view of a mixing system in accordance with one ormore aspects of the disclosure;

FIG. 13B-1 is a top view of a first impeller of the mixing systemfeatured in FIG. 13A;

FIG. 13B-2 is a side view of the first impeller;

FIG. 13C-1 is a top view of a third impeller of the mixing systemfeatured in FIG. 13A;

FIG. 13C-2 is a side view of the third impeller;

FIG. 14 is a perspective view of the interior of a fermentationapparatus in accordance with one or more aspects of the disclosure; and

FIG. 15A is a top view of one example of a sparge tube configuration inaccordance with one or more aspects of the disclosure;

FIG. 15B is a top view of a second example of a sparge tubeconfiguration in accordance with one or more aspects of the disclosure;

FIG. 15C is a top view of a third example of a sparge tube configurationin accordance with one or more aspects of the disclosure; and

FIG. 15D is side view of a sparge tube attached to a vessel inaccordance with one or more aspects of the disclosure.

DETAILED DESCRIPTION

In accordance with one or more embodiments, methods and systems forfermentation, e.g., aerobic fermentation, are provided. According to oneembodiment, the system includes at least one blower or turbine that isused in combination with a gas, such as air, and may include a diffuser,such as a sparge tube, for example, a cylindrical or circular spargetube, to introduce air bubbles into a vessel, e.g., a fermentationvessel containing a fermentation broth, e.g., including one or moremicroorganisms, such as one or more fungal cells. The methods andsystems disclosed herein provide a more cost-effective and efficientprocess for introducing a gas, e.g., air, into a process, such as afermentation process. The improved system, e.g., aerobic fermentationsystem, may therefore reduce the operating costs of a fermentation,especially when the fermentation time is very long, e.g., days or evenweeks. For example, the power requirements for delivering 1000 CFM(cubic feet per minute) at STP (standard temperature and pressure) usingthe blower or turbine system as disclosed herein is typically in therange of about 25-50 kW. In contrast, the same air that is suppliedusing a rotary compressor system will require power in the range ofabout 150-200 kW. For a 15,000 gallon fermentation vessel operating at0.5 vvm (vessel volumes per minute, which in this case is 7500 gallonsper minute or roughly 1000 CFM, and using an average cost of about $0.10per kWH, the costs are about $2.50/hour, or $60/day, or $600 for a10-day fermentation. A typical manufacturing plant may do 1000 suchfermentations a year, which would cost about $600,000 for theelectricity costs associated with the air. In contrast, the yearly costsfor a rotary compressor system would be about six times that amount, orabout $3,600,000.

The aspects disclosed herein in accordance with the present invention,are not limited in their application to the details of construction andthe arrangement of components set forth in the following description orillustrated in the accompanying drawings. These aspects are capable ofassuming other embodiments and of being practiced or of being carriedout in various ways. Examples of specific implementations are providedherein for illustrative purposes only and are not intended to belimiting. In particular, acts, components, elements, and featuresdiscussed in connection with any one or more embodiments are notintended to be excluded from a similar role in any other embodiments.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. Any references toexamples, embodiments, components, elements or acts of the systems andmethods herein referred to in the singular may also embrace embodimentsincluding a plurality, and any references in plural to any embodiment,component, element or act herein may also embrace embodiments includingonly a singularity. References in the singular or plural form are notintended to limit the presently disclosed systems or methods, theircomponents, acts, or elements. The use herein of “including,”“comprising,” “having,” “containing,” “involving,” and variationsthereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. References to “or” maybe construed as inclusive so that any terms described using “or” mayindicate any of a single, more than one, and all of the described terms.In addition, in the event of inconsistent usages of terms between thisdocument and documents incorporated herein by reference, the term usagein the incorporated reference is supplementary to that of this document;for irreconcilable inconsistencies, the term usage in this documentcontrols. Moreover, titles or subtitles may be used in the specificationfor the convenience of a reader, which shall have no influence on thescope of the present invention.

In accordance with certain embodiments, the fermentation processesdescribed herein may be part of a larger process, generally indicated at100 in FIG. 1, which is a flow diagram illustrating conversion ofbiomass feedstock to one or more products. In one particular embodiment,at act 110, the feedstock may be physically pretreated to reduce itssize, which is followed by e-beam irradiation to reduce itsrecalcitrance at act 120. At act 130, the feedstock is saccharified withone or more enzymes that may be produced via a fermentation process, asdiscussed below in reference to act 125, to form a sugar solution. Thesugar solution is then bioprocessed at act 140 in a fermentation processto produce a desired product, such as alcohol or an organic acid, suchas lactic acid, a salt of lactic acid, succinic acid or a salt ofsuccinic acid. Thus, according to various aspects, the fermentationsystem disclosed herein may be used for any fermentation product, suchas either the fermentation process at act 125 or at act 140. As noted inFIG. 1 at act 125, enzyme can be provided by a fermentation process(e.g., an aerobic fermentation), such as a fungal cell fermentationprocess, e.g., using Trichoderma reesei (T. reesei) such as strain RUTC30. Fungal cell fermentation processes can proceed for many days, e.g.,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or even 12 days or longer, and soreducing the cost of the provided air is advantageous to the cost of theenzyme. The resulting product from the fermentation process may besubjected to further processing, such as distillation, SMB (simulatedmoving bed) chromatography, or a form of electrodialysis, to produce afinal product at act 150. According to some embodiments,saccharification and fermentation may be performed in the same vessel.

Fermentation Overview

In accordance with one or more embodiments, fermentation is a biologicalprocess in which molecules, such as sugars, such as glucose, fructose,and sucrose are converted into other molecules, such as alcohols andmetabolic products, such as carbon dioxide and energy, in the form ofheat. For example, glucose and/or xylose can be fermented using one ormore bacteria, such as a lactobacillus to lactic acid, or glucose and anitrogen source can be co-fermented to produce peptides or polypeptides,such as proteins or enzymes. As shown in FIG. 2, for example, aqueoussugar solution is introduced into a vessel, and during fermentation theaqueous sugar solution, which functions as a carbohydrate substrate, isinoculated with a microorganism under aerobic conditions. The optimumgeneration of the microorganism requires solution of oxygen in theaqueous sugar solution to be at a rate sufficient to replace oxygenconsumed by the metabolic process. The rate of generation of themicroorganism, and hence the production capacity of the anaerobic vesselis largely limited by the rate of oxygen in solution. As shown in FIG.2, oxygen, in the case of an aerobic fermentation, may be introduced asfine bubbles into the aqueous sugar solution, which, as discussedfurther below, may be created by an air diffuser such as a sparge tube.In the case of an anaerobic fermentation, the gas introduced can be, forexample, carbon dioxide, nitrogen, argon, or even methane. Mixing of thesolution may be provided by an impeller, into the aqueous sugarsolution. Often the impeller (or at least one of the impellers in amixing system) utilized is suitable for “beating” the air or other gasinto solution because gases generally have a low solubility in liquids,for example on the order of 8 mg/L for the case of air in water. Such animpeller is often called a radial flow impeller and examples includeRushton impellers or Rushton type impellers. The rate of oxygen solutionis primarily a function of bubble surface area and time ofbubble-aqueous sugar solution contact. Generally, the oxygen transferrate may be improved by reducing bubble size, increasing shear, forexample, by using a radial flow impeller, increasing residence time,such as making a reactor with a high L to D ratio, or sandwiching aRushton type impeller between a down-pumping (on the top) and a uppumping (on the bottom) impeller. Other techniques are available, suchas using air with an enhanced oxygen level or pure oxygen (in the caseof an aerobic fermentation) or by reducing the temperature of thefermentation and thereby increasing the solubility of gases in thefermentation broth.

According to various embodiments, sugars, such as those produced bysaccharifying a cellulosic or lignocellulosic feedstock, and othermolecules, such as nitrogen sources, may be converted to one or moreuseful products, such as alcohols, such as sugar alcohols, e.g.,erythritol or xylitol, or other alcohols, such as butanol. Otherproducts, such as citric acid, lysine, glutamic acid, proteins, andenzymes can also be produced by contacting various fermentation brothswith one or more microorganisms. For example, Clostridium spp. may beused to convert sugars, such as fructose or glucose, to butanol.Clostridium spp. may also be used to produce ethanol, butyric acid,acetic acid, and acetone. Lactobacillus spp. may be used to producelactic acid. Other microorganisms, as discussed further below, may alsobe used during fermentation, including yeast and Zymomonas bacteria. Inaccordance with various aspects, saccharification may be partially orfully completed to produce a mixture that is subjected to fermentation.

According to various aspects, the fermentation process converts variousnutrients, such as an aqueous sugar solution produced from thesaccharification process to one or more products, such as a sugaralcohol. Non-limiting examples of such products include glycol,glycerol, erythritol, threitol, arabitol, xylitol, ribitol, mannitol,sorbitol, galactitol, iditol, inositol, volemitol, isomalt, maltitol,lactitol, maltotriitol, maltotetraitol, polyglycitol, butyric acid,gluconic acid, citric acid, and polyols, such as glycerin,pentaerythritol, ethylene glycol, and sucrose. Other products mayinclude amino acids, peptides, polypeptides, proteins, and enzymes.

Fermentation System Components

Referring to FIG. 3, a fermentation system in accordance with one ormore aspects of the disclosure and generally indicated at 300, isillustrated. As discussed further below, the fermentation system 300 mayinclude a vessel 302, a blower skid 304 that includes one or moreblowers 306, at least one inlet filter apparatus 310 for incoming airgenerated by the blower(s) 306, at least one sparge tube 312, acondenser 314, and an outlet filtration assembly 316.

Vessel

In accordance with various aspects, fermentation, such as fungal,bacterial or yeast cell fermentation, may be partially or completelyperformed in a vessel 302, as shown in FIG. 3. In certain embodiments,the aqueous sugar solution and/or other nutrients or fermentationadditives may be introduced to an inlet of the vessel, also referred toherein as a feed stream inlet, that may be positioned at the top of thevessel, the bottom of the vessel, or anywhere in between that issuitable for accomplishing the fermentation methods described herein. Asused herein, the term “vessel” broadly means any structure suitable forconfining one or more process components, including gas, liquid andsolid components and mixtures thereof. According to some embodiments,the vessel may be sized to have a volume of at least 1000 gallons. Forexample, the vessel may be sized to have a volume of 1500 gallons.According to another example, the vessel may be sized to have a volumeof 2500 gallons. According to other embodiments, the vessel may be sizedto have a volume of at least 10,000 gallons. For instance, the vesselmay be sized to have a volume of 15,000 gallons. According to someembodiments, the vessel may be sized to have a volume of at least100,000 gallons.

In accordance with certain embodiments, the vessel may not be highlypressurized, for example, not a certified ASME pressure vessel.According to certain embodiments, the pressure in the vessel may notexceed 12 psig, e.g., less than 10, 9, 8, 7, 6, 5, 4, 3.5, 3, 2.5, 2,1.5, or less than 0.5 psig. According to other embodiments, the vesselmay be closed or partially closed to operate under pressure, such asabove 1 bar, 1.5, 2.0, or 2.5 bar. In certain applications, the vesselmay be constructed to provide an anaerobic or aerobic environment forthe components such as the fermentation broth. The vessel may be sizedand shaped according to a desired application and volume of feed toprovide a desired volume of product output. The vessel may also compriseat least one outlet (as shown in FIG. 14), where product, such as sugaralcohol, protein(s), or enzyme(s), may be removed from the vessel.

According to various embodiments, the vessel may be constructed of anymaterial suitable for the purposes of the methods and systems describedherein. Non-limiting examples of suitable materials include steel,stainless steel, hastelloy, titanium, and aluminum. One or moreembodiments may include a vessel having one or more sidewalls dependingupon the desired shape of the vessel. For example a cylindrical vesselmay have one sidewall while a square or rectangular vessel may have foursidewalls. In certain embodiments, the vessel may have a cylindricalshape having one continuous sidewall positioned between the first andsecond walls. In certain other embodiments, the vessel may be closedwherein one or more sidewalls extend between a first wall and a secondwall. In accordance with at least one embodiment, the vessel may besized and shaped to have an aspect ratio L/D of 2:1 or less, e.g.,1.8/1, 1.6/1, 1.4/1, 1.2/1, 1/1, 0.8/1, 0.6/1, or less than 0.5/1.According to other embodiments, the vessel may have an aspect ratio of1:1. According to certain aspects, the size and shape of the vessel maybe designed to optimize or otherwise enhance the fermentation process.For example, a vessel with an aspect ratio of 2:1 may reflect the ratioof the volume of aqueous sugar solution to the volume of incoming air.For instance, a 12,000 gallon tank has a process requirement of 6000gallons of air that needs to be pumped in. Likewise, a 50,000 gallontank needs 25,000 gallons of air. According to certain embodiments, amaximum height of the vessel, measured as an average distance from thesparge tubes to the top of the fluid level is not more than 40 feet,e.g., less than 38, 37, 35, 33, 31, 29, 27, 25 or less than 20 feet whenthe blower is capable of generating 25 psig or less, e.g., less than 20,less than 19, 18, 17, 16, or 15 psig.

Sparge Tubes

One or more sparge tubes 312 or diffusers may also be positioned atvarious positions about the vessel 302. Although the sparge tubes 312are shown to be external to the vessel 302 shown in FIG. 3, each spargetube 312 connects to the inlet filter apparatus 310 and extends into thevessel and functions to inject fine bubbles into the fermentation brothfor the purposes of stimulating growth of the microorganisms. Accordingto various embodiments, the sparge tube may be constructed from aspecially sintered porous metal material. The sintered sparge tubematerials may be made by performing a hot isostatic pressing process,where high isostatic pressure is applied to constituent powderedmaterials in a perform at elevated temperatures, and the annealingprocess is terminated before completion. This results in a porousmaterial that is suitable for creating fine bubbles. Non-limitingexamples of suitable porous metals used for the sparge tube includestainless steel, stainless steel alloys (such as AISI 316L), titanium,nickel, and nickel alloys. According to some embodiments, the spargetube is constructed from a porous metal element, a threaded fitting, andin certain instances, a reinforcement rod. The sparge tubes may beflange-mounted to the side of the vessel. Sparge elements can be manydifferent shapes, including cylindrical or circular in shape. Inspecific embodiments, the sparge element is circular in shape, and isdistributed about the entire tank. According to certain embodiments, thepore size of the sparge tube is less than 100 microns, e.g., less than90, 80, 70, 60, 50, 40, 30, 20, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5,4, 3, 2, 1 or even less than 0.9 micron, e.g., 0.8, 0.7, 0.6, 0.5, 0.4or even less than 0.25 microns. According to certain embodiments, forexample to minimize pressure drop, the porosity of the sparge element isgreater than 50 percent, e.g., greater than 60, 70, 80, 85, 88, 90 oreven greater than 95 percent porosity. As shown in FIG. 3, four spargetubes 312 may be positioned at equidistant locations around theperimeter of the vessel 302. The sparge tubes 312 may also be positionedto introduce air into a lower portion of the vessel 302 and the bottomof the fermentation broth held within, which allows for a more efficientdistribution of air, as opposed to placing the air inlets near the topof the vessel 302. As will be appreciated, the number of sparge tubesmay be increased or decreased according to the size of the vessel andthe process requirements. The sparge tubes may be configured to createmicro-sized bubbles in one direction, multiple directions, or in alldirections, such as in a 360 degree arrangement.

Referring to FIGS. 15A-15D, several different examples of sparge tubesare shown that are suitable for one or more of the processes and systemsdisclosed herein. FIG. 15D is a general illustration of how the spargetube 312 is attached to a vessel 302. The configuration shown in FIG.15A is a top view of an example of one sparge tube positioned within atank 302, and the configuration shown in FIG. 15B is a top view of anexample of several sparge tubes positioned within a tank 302. The spargetubes of FIGS. 15A and 15B are generally cylindrical in shape, andextend into the vessel 302 in linear or straight lengths, and in thisinstance the sparge tubes expand across the entire width of the vessel,although, other lengths are also within the scope of this disclosure,such as the sparge tubes shown in FIG. 14, which extend partially (andslightly downward) into the vessel. In contrast, the sparge tube shownin FIG. 15C is bent to extend in a circular shape that generally followsthe circumference of the interior of the vessel. As shown, the spargetube of this configuration may be positioned in close proximity to theinterior walls of the vessel 302.

Blower Skid Components

In accordance with one or more embodiments, the fermentation system mayinclude a blower skid 304, as shown in FIGS. 3-6, that supplies a gas,such as oxygen or air, to the fermentation broth in the vessel 302. Theblower skid 304 includes at least one blower 306 and a heat exchanger308. The blower skid 304 may also include at least one pressure gauge,318 and 324, at least one temperature gauge 320, and at least one flowmeter 322. According to some embodiments, the fermentation system 300may include at least one power operated blower 306. Each centrifugal gasturbine-driven blower 306 includes a driver motor equipped with a rotorthat spins at high speeds and functions to discharge gas, such as air,into the vessel. In accordance with at least one embodiment, each blowermay be sized according to the process requirements and the size of thevessel. For example, according to one embodiment, each blower mayinclude a 12.5 hp motor. The size of the blower dictates the amount ofair in cubic feet per minute that can be sparged into the vessel. Asnoted above, a 12,000 gallon vessel may have a process requirement of1000, 2000, 3000, 4000, 5000, or 6000 or more gallons of air per minute,which in turn dictates the sizing of the blowers. For example, inaccordance with various aspects, fermentation may be performed withaeration using a sparging tube, as discussed above, and an air and/oroxygen supply to maintain the dissolved oxygen level above about 10%,such as above 20%. Further, the air requirement may be distributed tomultiple blowers instead of using one single blower, since the singleblower may be significantly more expensive to purchase and operate. Forexample, the fermentation system of FIG. 3 uses two 11 kW blowersinstead of a single 22 kW blower. Further, the blower may be selected tooperate with a maximum psi. For instance, the blower may produce amaximum pressure of 20 psi. According to some embodiments, a suitableblower may be available from Spencer Turbine Co., Windsor, Conn., suchas a Spencer 2500 Series blower, including the Spencer Model NumberCS21R96. The use of one or more blowers to drive air into the vessel ismore cost effective and more efficient than using compressors. Forexample, compressors are expensive to manufacture, maintain, andoperate, and may incur energy costs that are at least four times, e.g.,six times, that of one or more blowers.

In accordance with at least one embodiment, the air exiting theblower(s) 306 passes through a water-cooled heat exchanger 308 beforeentering the inlet filter apparatus 310 (discussed further below) andthe vessel 302. According to some embodiments, multiple heat exchangersmay be utilized. For example, one heat exchanger may be used for coursetuning and a second heat exchanger may be used for fine tuning theexiting temperature of the gas. For instance, the first heat exchangermay run a cooling fluid, such as water, that is at a temperature between80° F. and 110° F., such as between 85° F. and 100° F., and the secondheat exchanger may run a fluid that is at a temperature of less than 65°F., e.g., less than 60° F., 58° F., or less than 55° F. According tosome embodiments, air entering the blower 306 may be at room temperatureC25° C.), and is then heated to a temperature of 200° F. or more by theblowers. According to various embodiments, the heat exchanger 308functions to cool down the air or other gas entering into the vessel 302so that it does not kill the organisms and/or raise the temperature ofthe batch or other processing occurring in the vessel. Thus, airentering the heat exchanger 308 may be at a temperature of 200° F. ormore, which is then cooled down to a temperature below 100° F., such as90° F., 85° F., 80° F., and in certain instances, back to roomtemperature of 25° C. by the heat exchanger 308. The size of the heatexchanger 308 is a function of the flow rate of air going into thevessel 302. Other cooling fluids besides water used by the heatexchanger 308 may include refrigerant and cryogenic liquids. The heatexchanger 308 may be a shell and tube heat exchanger, where coolantfluid flows inside the tubes, and the air or other gas flows across thefins. As will be recognized by one of ordinary skill in the art, othertypes of heat exchangers are also within the scope of this disclosure.According to some embodiments, the heat exchanger 308 is a tube and fintype heat exchanger. For example, both the tubes and the fins may beconstructed from stainless steel, or the tube may be constructed fromstainless steel and the fins may be constructed from aluminum material.In still other embodiments, the tubes and the fins may be made fromcopper.

As shown in FIGS. 3-5, the blower skid 304 may also include one or morepressure gauges 318 and 324, temperature gauges 320, and flow meters322. For instance, temperature and pressure readings may be taken of theheated air exiting the blower by temperature gauge 320 and pressuregauge 318. As shown in FIGS. 4 and 5, a check valve 328 may be also beincluded in the blower skid assembly to prevent reverse flow. The flowrate of the air moving to the fermentation vessel 302 may be measured bythe flow meter 322. A second pressure gauge 324 may also measure thepressure of the air before it is split into multiple flowpaths anddistributed to the inlet filter apparatuses 310, as discussed furtherbelow.

Inlet Filter Apparatus

According to certain embodiments the fermentation system includes atleast one filter apparatus 310, also referred to herein as an inletfilter apparatus, as shown in FIGS. 3, 8, and 9. Gas such as air oroxygen that exits the blower 306 and heat exchanger 308 and isintroduced into the fermentation process may first need to be sterilizedso as to not interfere with the fermentation chemistry. According to theembodiment shown in FIG. 3, air exiting the blower skid assembly 304 issplit into multiple flowpaths, such as the four separate flowpaths shownin FIG. 3, using flexible conduits. Each of the flexible conduits may besized to avoid creating large pressure drops. For example, the flexibleconduits may be sized to have a diameter that is at least two inches.Each flowpath is equipped with a filter apparatus 310, as shown moreclearly in FIGS. 8 and 9. Each filter apparatus may include a membranefilter. The porosity of the membrane filter may be from about 50 percentto about 95 percent, e.g., between about 60 percent and about 80 percentand the pore size may be between about 0.1 microns and 2 microns, suchas between 0.2 microns and 1 micron. For example, warmed air from theblower skid assembly 304 may be forced through a filter that removes airparticles and bacteria and many viruses down to 0.2 microns. Placementof the inlet filter apparatus 310 at the outlet side of the blower skid304, including the heat exchanger 308, rather than at the inlet sidebefore the blower, assures that air passing through the filter is underpositive pressure relative to ambient. Any leak following or before thefilter will therefore not serve as a path for particulate entry to theairstream. The membrane may be constructed from any one or morehydrophobic materials, including polymers. Suitable filters include thepolytetrafluoroethylene (PTFE) Pall Emflon™ filter (Pall Corporation,East Hills, Long Island, N.Y.).

The inlet filter apparatus 310 may include several other componentsbesides the membrane filter. For example, FIGS. 8 and 9 illustrate apressure and temperature gauge that may be used to measure the pressureand temperature of the incoming air from the blower skid 304. This airmay pass through the filter, where it is sterilized. A second pressuregauge measures the pressure of the air exiting the filter, before it issent through a check valve (to prevent backflow and contamination) andonward into the vessel 302.

Referring to FIG. 3, the fermentation system 300 may include four inletfilter apparatuses 310 that are positioned at equidistant positionsaround the perimeter of the vessel 302, as described above in referenceto the sparge tubes 312. The number of inlet filter apparatuses 310 maybe a function of one or more process parameters, such as the volume offermentation broth that is to be treated, the type of microorganism usedin the process, which may dictate the necessary amount of air or oxygenneeded for the process, and the size and/or shape of the tank. As shownin FIG. 3, each inlet filter apparatus 310 may be configured to connectto a sparge tube 312 that extends into the vessel 302. In someembodiments, the sparge tube 312 may connect to the inlet filterapparatus 310 at a position external to the tank, such as in instanceswhere the sparge tube includes a fluid-tight connector that may be usedfor mating different components of the system together. In otherembodiments, the sparge tube 312 is positioned completely within theinterior of the vessel 302, so that a connecting region, such as a pipe,extends through the vessel 302 and connects to the filter apparatus atone end and connects to the sparge tube 312 at the other end. The top ofthe inlet filter apparatus 310 may also include one or more cables orother attachment means that can be used to attach and stabilize the topof the filter cartridge to the vessel 302, as shown in FIGS. 3, 8, and9.

Condenser for Vessel

According to various embodiments, the fermentation system 300 may alsoinclude a condenser 314, which functions to condense fluid back into thetank. The condenser 314 is illustrated in FIGS. 3, 10A, and 10B.Pressure within the vessel 302 created from sparging causes water todischarge from the vessel 302. In addition, water particles atomizedduring sparging need to be contained or otherwise prevented fromentering the outlet filtration assembly 316 (discussed below), so as toprevent water from condensing in the filters. Therefore, the condenser314 may be positioned at the top of the vessel and used to condense thesparge bubbles that float from the bottom to the top of the vessel 302.According to various aspects, the condenser 314 may be equipped withmultiple tubes that are cooled by the surrounding ambient air; therebyallowing the sparge bubbles to condense as water, and flow back into thevessel 302. According to certain embodiments, air exiting the condenser314 is further heated so as to drive off any moisture before it entersthe outlet filtration assembly 316.

In accordance with some embodiments, the condenser may be a shell andtube condenser. According to some embodiments, the condenser is a tubeand fin type condenser. For example, both the tubes and the fins may beconstructed from stainless steel, or the tube may be constructed fromstainless steel and the fins may be constructed from aluminum material(for greater efficiency). In still other embodiments, the tubes and thefins may be made from copper.

Outlet Filtration Assembly

In accordance with at least one embodiment, the fermentation system 300includes a filtration assembly 316, also referred to herein as an outletfiltration assembly. The outlet filtration assembly may serve a numberof functions, including keeping bacteria and other contaminants fromreverse-flowing back into the vessel 302. The outlet filtration assembly316 may include several filters, such as those discussed above inreference to the inlet filter apparatus 310. According to certainembodiments, the outlet filtration assembly 316 may be in fluidcommunication with the condenser 314 via a conduit, which may be heated.For example, not all water escaping from the vessel may be captured andre-condensed back into the vessel by the condenser 314. Therefore,additional water may be heated in the conduit so as to evaporate allremaining liquid. In accordance with some embodiments, air that exitsthe outlet filtration assembly vents to the atmosphere, and in certaininstance may be vented to an external environment.

Impeller/Agitator for Vessel

In reference to FIGS. 13A, 13B-1, 13B-2, 13C-1, and 13C-2, the interiorof the vessel may be equipped with a mixing system 326 that functions tomechanically mix the contents of the vessel and to maximize oxygentransfer. According to some embodiments, the mixing system 326 mayinclude one or more impellers. The mixing system 326 may be verticallypositioned in the center of the vessel 302. The mixing system 326 may bedriven by a motorized central shaft that includes vertically-positionedimpeller blades. For example, as shown in FIG. 13A, a first impeller maybe positioned in an upper portion of the interior of the vessel, asecond impeller positioned near the center of the vessel, and a thirdimpeller may be positioned in a lower portion of the vessel. A top andside view of the first impeller are shown in FIGS. 13B-1 and 13B-2,respectively, and a top and size view of the third impeller are shown inFIGS. 13C-1 and 13C-2, respectively. Each impeller may be configured toserve a different function. In the configuration shown in FIG. 13A, thefirst (top) and third (bottom) impellers increase residence time of airsparged into the vessel by keeping air trapped in the spacing betweenthese two impellers. For instance, the bottom impeller is configured tocreate a lifting or rising force, which is counteracted by the pushingor lowering force of the top impeller. The second, middle impeller maybe a Rushton turbine, as discussed above, which creates radial-flow highshear forces that “beat” or otherwise enhance gas dissolution into thesurrounding fermentation broth. The speeds used for each of theimpellers may depend on the size of the vessel and the type ofprocessing. For example, the speed of the impellers for a 2500 gallontank may be less than 100 rpm, for example, less than 80, 70, 60, orless than 50 rpm. The impeller blades are constructed from a materialthat does not interfere with the chemical fermentation process, such asa metal, including steel or a metal alloy. The mixing system 326 mayalso be equipped with a variable speed controller, so that speed of oneor more of the impellers can be adjusted during the fermentationprocess. A motor, such as a 15 hp motor, may be used to drive thecentral shaft.

The mixing system 326 may be sized and shaped to fit within the interiorof the vessel 302. For instance, according to one example, the firstimpeller may have a diameter of 23 inches (584 mm), the second impellermay have a diameter of 34 inches (864 mm), and the third impeller mayhave a diameter of 12.8 inches (325 mm). Further, the distance betweenthe horizontal center line of the first impeller and the horizontalcenter line of the second impeller may be 30 inches (762 mm) and thedistance between the horizontal center line of the second impeller andthe horizontal center line of the third impeller may be 22 inches (559mm). The diameter of the shaft above the first impeller and extendingdown through the second impeller may be 2.5 inches (64 mm). The sectionof the shaft above the third impeller may have a diameter of 1.5 inches(38 mm). As will be appreciated, other sizes and configurations of themixing system 326 and its components are also within the scope of thisdisclosure. The sizes may be varied according to the size of the vesseland the type of application.

In reference to FIG. 14, an interior of a fermentation vessel 302 isshown that includes a mixing system 326 that includes threevertically-positioned impeller blades, such as those discussed above inreference to FIG. 13A, which appear as cylinders in FIG. 14. Alsoincluded is a view of four sparge tubes 312 positioned around theperimeter of the vessel 302 and extend slightly downward into a centralbottom portion of the vessel. As discussed above, each sparge tube 312may deliver uniform small bubbles to the fermentation broth that promotethe growth of the microorganisms in the fermentation broth.

Fermentation Process Overview and Conditions

Referring to FIG. 7, a schematic representation of the aerobicfermentation system 300 shown in FIG. 3 is shown. During operation,aqueous sugar solution is pumped into the fermentation vessel 302through an inlet (not shown in FIG. 7). In some embodiments, the inletmay be injected into one or more ports positioned in an upper portion ofthe vessel, and in certain instances, the broth may be introduced intoany port that is above the fluid line within the vessel. According tosome embodiments, the fermentation is performed using a glucose solutionhaving an initial glucose concentration of at least 5 wt. % at the startof fermentation. Furthermore, the glucose solution can be diluted afterfermentation has begun.

In accordance with various embodiments, the fermentation process may beperformed according to a method of continuous operation using multiplebatches. For example, the completion of a fermentation process may beindicated by one or more of the following properties of the fermentationbroth: the concentration of nutrients, the concentration of one or moreproducts, the pH, the amount of dissolved gas, and the fermentation timeperiod.

According to certain aspects, a high initial sugar concentration at thestart of fermentation may favor the production of sugar alcohols. Thus,the saccharified feedstock solution may be concentrated prior tocombination with a microorganism that produces sugar alcohols toincrease the glucose level of the solution. Concentration may be done byany desired technique, for example, by heating, cooling, centrifugation,reverse osmosis, chromatography, precipitation, crystallization,evaporation, adsorption, and combinations thereof. According to someembodiments, concentration is performed by evaporation of at least aportion of the liquids from the saccharified feedstock. In certainaspects, concentration increases the glucose content to greater thanabout 5 wt %, greater than about 10 wt. %, greater than about 20 wt. %,greater than about 30 wt. %, greater than about 40 wt. % and greaterthan about 50 wt. %.

According to at least one embodiment, the saccharified feedstock may bepurified before or after concentration. Purification may be performed toincrease the glucose content to greater than about 50 wt. % of allcomponents other than water, such as greater than about 60 wt. %,greater than about 70 wt. %, greater than about 80 wt. %, greater thanabout 90 wt. %, and greater than about 99 wt. %. Purification may beperformed by any technique known in the art, non-limiting examplesincluding heating, cooling, centrifugation, reverse osmosis,chromatography, precipitation, crystallization, evaporation, adsorption,or any combination thereof.

Once in the vessel 302, the aqueous sugar solution may be contacted withone or more microorganisms, as discussed further below. According to atleast one embodiment, the microorganisms are cannulated into the vesselfrom a prior process, such as from the final vessel of a seed trainprocess. In some embodiments, the contacting step includes a dual stageprocess, comprising a cell growth step and a fermentation step. Forexample, a dual stage fermentation process may include an initial cellgrowth phase followed by a product production phase. In the growthphase, the process conditions may be selected to optimize cell growth,where as in the production phase, process conditions may be selected tooptimized production of one or more desired fermentation products.Generally speaking, low sugar levels, such as those between 0.1 and 10wt. %, or between 0.2 and 5 wt. % in the growth medium favors cellgrowth, and higher sugar levels, such as those greater than about 5 wt.%, greater than about 10 wt. %, greater than about 20 wt. %, greaterthan about 30 wt. %, and greater than about 40 wt. % in the fermentationmedium favors product production. In addition, other process parametersmay be modified for each stage. For example, temperature, agitation,sugar levels, nutrients, and/or pH may all be adjusted according to thestage of the process. In addition, process conditions may be monitoredin each stage for the purposes of optimizing the process. For example,the cell growth stage of the process may be monitored to achieve anoptimum density, for example, about 50 g/L, greater than about 60 g/L,greater than about 70 g/L, or greater than about 75 g/L, and aconcentrated saccharified solution may be added to trigger the onset ofproduct formation. Optionally, the process may be optimized, forexample, by monitoring and adjusting the pH or oxygenation level withprobes and automatic feeding to control cell growth and productformation. According to a further aspect, other nutrients may becontrolled and monitored to optimize the process, such as amino acids,vitamins, metal ions, yeast extract, vegetable extracts, peptones,carbon sources and proteins.

Dual-stage fermentations are described in Biotechnological production oferythritol and its applications, Hee-Jung Moon et al., Appl. Microbiol.Biotechnol. (2010) 86: 1017-1025. In certain instances a high initialconcentration of glucose at the start of the fermentation favorserythritol production, but if a high concentration is maintained for toolong, it may be detrimental to the microorganism. A high initial glucoseconcentration may be achieved by concentrating glucose during or aftersaccharification as discussed above. After an initial fermentationperiod that allows the start of fermentation, the fermentation media maybe diluted with a suitable diluent to bring the level of glucose belowabout 60 wt. %, below about 50 wt. %, or below about 40 wt. %. Thediluent may be water or water with additional components such as aminoacids, vitamins, metal ions, yeast extract, vegetable extracts,peptones, carbon sources and proteins.

Referring back to FIG. 7, the fermentation process may be performed withaeration using a sparging tube and an air and/or oxygen supply tomaintain the dissolved oxygen level in the fermentation broth aboveabout 10%, such as above 20%. This may be achieved by taking roomtemperature air and passing it through one or more blowers, which createthe necessary force to push the air through the heat exchanger 308, theinlet filter apparatus 310, and the sparge tubes 312 positioned in thevessel 302. Air exiting the blowers is heated from room temperature toabout 200° C. using heat exchanger 308, as described above, and thensplit into four flowpaths. Air passing through each flowpath is firstpassed through a 0.2 micron filter in the inlet filter apparatus 310 toremove contaminants, before being introduced into the fermentation broththrough the sparge tube 312.

As discussed above, the fermentation vessel 302 may be sized and shapedto optimize one or more process conditions. For example, in certaininstances the maximum air pressure that can be generated by theblower(s) 306 is 20 psi. In order to get this air to the top regions ofthe vessel 302, the vessel may be shorter, since a taller tank wouldcreate high hydrostatic pressure. According to some embodiments, thevessel may not be pressurized, but may be equipped with one or moresteam jets that may be used for the purposes of sterilization. The steammay be injected using a large diaphragm valve, which may pressurize thevessel to about 0.5 psi, or in the alternative, the steam may beinjected with one or more valves open to atmosphere, so that the vesselremains at atmospheric pressure.

Referring to FIG. 3, pressure in the fermentation vessel 302 may becontrolled by one or more pressure relief valves 330 that include apressure gauge. The pressure relief valve may be controlled by acontroller, as discussed further below, and functions to releasepressure from the vessel 302 when the pressure within the vessel 302exceeds a predetermined value, such as 2 psi. The pressure relief valve330 shown in FIG. 3 extends across the entire diameter of the tank andincludes two pressure gauges positioned on the top of the vessel.

In accordance with various embodiments, jet mixing may be used duringfermentation. The jet mixing may be performed by one or more impellers,such as the mixing system 326 discussed above in reference to FIG. 13A.The impeller(s) functions to mix the contents of the vessel 302 and toenhance oxygen transfer to the microorganisms.

In accordance with some embodiments, fermentation may be performed at apH in a range of pH 4 to 7. The pH may be maintained in a certain rangeof values depending on the type of microorganism used. For example, whenusing yeast as a microorganism, the pH is maintained in a range of pH4-5, whereas the pH is maintained in a range of pH 5-6 when Zymomonas isused. According to some embodiments, the pH of the fermentation broth ismeasured using a pH probe that is positioned in the side of the vessel.In certain embodiments, ammonium hydroxide may be added to maintain thepH at a desired level.

According to some embodiments, fermentation may be performed for apredetermined time. For example, the fermentation may be conducted from24 to 168 hours, such as from 24 to 96 hours, or from 24 to 120 hours.

In accordance with various embodiments, fermentation is performed attemperatures in the range of 20° C. to 40° C. (e.g., 26° C. to 40° C.).The temperature may depend on the type of microorganism used. Forexample, thermophilic microorganisms prefer higher temperatures.According to various embodiments, nutrients for the microorganisms maybe added during the fermentation process. For example, food-basednutrient packages such as those described in U.S. Pat. No. 8,852,901,the entire disclosure of which is incorporated herein by reference.

In accordance with various embodiments, the product from thefermentation process is isolated. For example, product may be extractedfrom one or more outlets of the vessel, which in certain instances maybe positioned at the bottom of the vessel, as shown in FIG. 14.

As discussed above, a condenser 314 may be positioned at the top of thevessel 302 the functions to condense the sparge bubbles that float tothe top of the vessel 302. Further, the vessel may also be equipped withat least one vent 332 that allows gases, such as carbon dioxide, oxygen,and/or air to escape the vessel 302.

According to some embodiments, the fermentation system includes acontroller that may be used to control one or more aspects of thefermentation process and/or equipment. For example, each inlet filterapparatus 310 may be configured to measure the temperature and pressureof the incoming air or other gas into the vessel 302. Further, the rpmof each blower may also be monitored, as well as the pH and the amountof dissolved oxygen in the fermentation broth. A predetermined value orrange of values may be desired for each of these process variables, andwhen the measured value falls below or above the predetermined value,the controller may be configured to adjust one or more aspects of thefermentation process. For example, if the level of dissolved oxygen inthe fermentation falls below 10%, then the rpm of the blower may beincreased to push more air into the vessel.

In accordance with certain embodiments, all or a portion of thefermentation process may be interrupted before the low molecular weightsugar is converted to an alcohol such as ethanol. Intermediatefermentation products include sugar and carbohydrates, which may be inhigh concentration. The sugars and carbohydrates may be isolated via anymeans known in the art. According to various aspects, these intermediatefermentation products may be used in the preparation of food for humanor animal consumption. Additionally or alternatively, the intermediatefermentation products can be ground to a fine particle size, forexample, using a stainless-steel laboratory mill, to produce aflour-like substance.

In accordance with one or more embodiments, a mobile fermenter may beused for the fermentation process, as described in International App.No. PCT/US2007/074028 and published as PCT Publication WO 2008/011598,the disclosure of which is hereby incorporated by reference in itsentirety. According to a further embodiment, all or a portion of thefermentation process may be performed during transit.

According to other embodiments, anaerobic organisms may be used in thefermentation process. Thus, the fermentation process may be conducted inthe absence of oxygen. The fermentation process may be conducted in thepresence of one or more inert gases, such as nitrogen (N₂), argon (Ar),helium (He), carbon dioxide (CO₂), and mixtures thereof. Further, thefermentation mixture may have a constant purge of an inert gas flowingthrough the vessel during part or all of the fermentation process.According to one embodiment, carbon dioxide is used to achieve ormaintain anaerobic conditions during the fermentation process, withoutany addition of any other inert gas.

Fermentation Agents

In accordance with various embodiments, the microorganisms used in thefermentation process may be naturally occurring microorganisms and/orengineered microorganisms. For example, the microorganism may be abacterium, such as cellulolytic bacterium, a fungus, such as yeast, aplant, a protist, such as a protozoa or a fungus-like protist, such as aslime mold, or an alga. When the microorganisms are compatible, mixturesof microorganisms may be used for fermentation.

The microorganism used for fermentation may be any suitablemicroorganism capable of converting carbohydrates, such as glucose,fructose, xylose, arabinose, mannose, galactose, oligosaccharides, orpolysaccharides into fermentation products. According to variousaspects, the fermentation microorganisms include strains of the genusSaccharomyces spp. (including, but not limited to, S. cerevisiae(baker's yeast), S. distaticus, S. uvarum), the genus Kluyveromyces,(including, but not limited to, K. marxianus, K. fragilis), the genusCandida (including, but not limited to, C. pseudotropicalis, and C.brassicae), Pichia stipitis (a relative of Candida shehatae), the genusClavispora (including, but not limited to, C. lusitaniae and C.opuntiae), the genus Pachysolen (including, but not limited to, P.tannophilus), the genus Bretannomyces (including, but not limited to,e.g., B. clausenii (Philippidis, G. P., 1996, Cellulose bioconversiontechnology, in Handbook on Bioethanol: Production and Utilization,Wyman, C. E., ed., Taylor & Francis, Washington, D.C., 179-212)). Othersuitable microorganisms include, for example, Zymomonas mobilis,Clostridium spp. (including, but not limited to, C. thermocellum(Philippidis, 1996, supra), C. saccharobutylacetonicum, C. tyrobutyricumC. saccharobutylicum, C. Puniceum, C. beijernckii, and C.acetobutylicum), Moniliella spp. (including but not limited to M.pollinis, M. tomentosa, M. madida, M. nigrescens, M. oedocephali, M.megachiliensis), Yarrowia lipolytica, Aureobasidium sp.,Trichosporonoides sp., Trigonopsis variabilis, Trichosporon sp.,Moniliellaacetoabutans sp., Typhula variabilis, Candida magnoliae,Ustilaginomycetes sp., Pseudozyma tsukubaensis, yeast species of generaZygosaccharomyces, Debaryomyces, Hansenula and Pichia, and fungi of thedematioid genus Torula (e.g., T. corallina).

Many such microbial strains are publicly available, either commerciallyor through depositories such as the ATCC (American Type CultureCollection, Manassas, Va., USA), the NRRL (Agricultural Research ServiceCulture Collection, Peoria, Ill., USA), or the DSMZ (Deutsche Sammlungvon Mikroorganismen and Zellkulturen GmbH, Braunschweig, Germany), toname a few.

According to some embodiments, the microorganism used for fermentationmay include a yeast. Commercially available yeasts include, for example,RED STAR®/Lesaffre Ethanol Red (available from Red Star/Lesaffre, USA),FALK) (available from Fleischmann's Yeast, a division of Burns PhilipFood Inc., USA), SUPERSTART® (available from Alltech, now Lalemand),GERT STRAND® (available from Gert Strand AB, Sweden) and FERMOL®(available from DSM Specialties).

In accordance with various embodiments, microorganisms that are suitableto saccharify the biomass material and produce sugars may also be usedin the fermentation process for the purposes of converting those sugarsinto useful products.

EXAMPLES

The systems and methods described herein will be further illustratedthrough the following examples, which are illustrative in nature and arenot intended to limit the scope of the disclosure.

Example Aeration Blower System

An example of a blower system suitable for use in the fermentationprocesses and systems discussed herein includes two Spencer 2500 SeriesPower Mizer High Efficiency Multistage Centrifugal Cast Blowers, ModelNumber CS21R96, available from Spencer Turbine Co. (Windsor, Conn.).Each of the blowers is rated 650 ICFM at 11 psig and include a six inchflanged inlet and a five inch flanged outlet. Each blower is powered bya 50 HP, 460 Volt, three-phase, 60 Hz, 3600 rpm, TEFC motor.

The blower system also includes a common water-cooled heat exchanger(HEX) with 304 SS housing, 304L SS casing, 304 SS (8 inch) flanged airinlet and outlet, and 1.5 inch copper flanges for the water supplylines. An example of the water-cooled heat exchanger includes theC-Series, Model Number C-125 available from Xchanger, Inc. (Hopkins,Minn.). The heat exchanger is a fin-tube assembly constructed fromcopper tubes and aluminum fins. The performance metrics for this heatexchanger are outlined below in Table 1:

TABLE 1 Performance Metrics of HEX Process Media Side Service Media SideFluid Air Water Circulated Volumetric 1,100.0 Std. ft3/min. 42.9gal/min. Flow Rate Total Fluid 4,933.5 lb/hr 21,401.9 lb/hr EnteringLiquid 21,401.9 lb/hr Water Vapor 27.4 lb/hr Non- 4,906.1 lb/hrCondensibles Vaporized or (Cond.) Temperature In 266.0° F. 60.0° F.Temperature 86.0° F. 70.0° F. Out Inlet Pressure 25.696 lb/in2(Absolute) Velocity 1,013.8 ft/min 5.0 ft/sec (Standard) Pressure Loss0.11 lb/in2 2.0 lb/in² Fouling Factor 0.00010 ft2-° F.-hr/BTU 0.00100ft²-° F.-hr/BTU Total Heat Exchanged: 214,284 BTU/hr

In addition, the heat exchanger has a design temperature and pressure of300° F. and 12.0 lb/in² for the process media side and 200° F. and 100.0lb/in² for the service media side, respectively.

One or more valves are also included in the blower system, includingmodulating (6 inch) valves (e.g., 4-20 mA), butterfly valves (6 inch),check valves (6 inch), a water solenoid valve for the heat exchanger,and a temperature control valve to maintain the heat exchanger dischargetemperature. Also included are five inch flanges with six inch flangecompanion adapters, and six inch flanged expansion joints. A six inchinlet silencer/filter assembly is also included for use with the blower.

The blower system also includes one or more sensors and other measuringor process feedback devices. For example, the system includes at leastone RTD (Resistance Temperature Detector) sensor and transmitter forinboard and outboard blower bearings, as well as for the inlets andoutlets of the heat exchanger. The inboard and outboard lower bearingsalso include vibration sensors and transmitters. An RTD device and apressure sensor are also used to measure the temperature and pressure ofthe common discharge. One or more flow meters are also used to measurethe air flow rates.

A common EMBC anti-surge system is also used in combination with theblower system, and includes a motor actuated air-bleed valve, NEMA 4actuator, and an inline TEE air silencer fitted with a protectivescreen.

A NEMA 12 control panel is also included with the system.

The fermentation system described herein may be used for celluloseenzyme production and has a production rate of approximately 1 g/L perday.

In accordance with the system described above, a cellulase fermentationwas run with the media volume of approximately 1,600 gal. The majorcomponents of the fermentation media were corn cob, rice bran, andammonium sulfate where corn cob was the main inductant. The fermentationwas inoculated with 5% (V/V) of seed inoculum, and the reactor wassparged with air at ⁻64 sCFM (⁻0.3 VVM) while agitated at ⁻63 RPM for 10days. The pH was kept above 3.8, and the temperature was at 27±3° C. forthe entire run. The titer of the product was approximately 11 g/L.

Having thus described several aspects of at least one example, it is tobe appreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. For instance, examplesdisclosed herein may also be used in other contexts. Such alterations,modifications, and improvements are intended to be part of thisdisclosure, and are intended to be within the scope of the examplesdiscussed herein. Accordingly, the foregoing description and drawingsare by way of example only.

1. A system for delivering air to an aqueous liquid for aerobic fermentation of the aqueous liquid, comprising: a vessel having a length to diameter ratio of less than 2:1; an aeration system including at least one sparge tube having a pore size of less than 5 microns and a porosity of greater than 50 percent in fluid communication with an interior of the vessel; at least one blower configured to deliver air at a pressure of less than 15 psig to the at least one sparge tube; and a heat exchanger in fluid communication between the at least one blower and the at least one sparge tube that cools the air to below 100° F. (37.8° C.) prior to entering the at least one sparge tube.
 2. The system of claim 1, wherein the at least one sparge tube is constructed from a sintered, porous metal.
 3. The system of claim 1, wherein the at least one sparge tube is positioned in a lower portion of the vessel.
 4. The system of claim 3, wherein the at least one sparge tube is mounted to a sidewall of the vessel.
 5. The system of claim 1, wherein the vessel has a volume of at least 10,000 gallons.
 6. The system of claim 1, further comprising at least one filter configured to filter air delivered from the at least one blower to the at least one sparge tube.
 7. The system of claim 6, wherein the system includes a plurality of sparge tubes and a plurality of filters positioned at equidistant positions around a perimeter of the vessel such that each sparge tube of the plurality of sparge tubes is paired with a filter of the plurality of filters.
 8. The system of claim 7, wherein the plurality of sparge tubes and the plurality of filters connect at a positions external to the vessel.
 9. The system of claim 6, wherein the heat exchanger has an inlet in fluid communication with an outlet of the blower and an outlet in fluid communication with the at least one filter.
 10. The system of claim 9, further comprising flexible conduit material coupled to the at least one filter and the heat exchanger.
 11. The system of claim 1, further comprising at least one condenser in communication with an interior of the vessel and configured to condense sparge bubbles.
 12. The system of claim 11, wherein the at least one condenser is positioned at a top of the vessel.
 13. The system of claim 12, further comprising an outlet filtration assembly in fluid communication with the at least one condenser.
 14. The system of claim 1, further comprising a mixing system positioned within the interior of the vessel.
 15. The system of claim 14, wherein the mixing system includes a top impeller configured to generate a lowering force and a bottom impeller configured to generate a lifting force within the aqueous liquid.
 16. The system of claim 1, wherein the aeration system is configured to maintain a dissolved oxygen concentration of at least 10% in the aqueous liquid.
 17. The system of claim 1, wherein a distance from the at least one sparge tube to a top surface of the aqueous liquid is not more than 40 feet.
 18. A system for providing air to a fermentation process, comprising: a fermentation broth disposed in a vessel having a length to diameter ratio of less than 2:1; an aeration system that maintains a dissolved oxygen concentration of at least 10% in the fermentation broth, the aeration system including a sparge tube in fluid communication with the fermentation broth and having a pore size of less than 5 microns and a porosity of greater than 50 percent; at least one blower in fluid communication with the fermentation broth, the at least one blower configured to deliver air at a pressure of less than 15 psig into the vessel through the sparge tube for aerobic fermentation of the fermentation broth; and a heat exchanger in fluid communication between the at least one blower and the sparge tube that cools the air to below 100° F. (37.8° C.) prior to entering the sparge tube.
 19. The system of claim 18, wherein the at least one blower includes a driver motor equipped with a rotor.
 20. The system of claim 18, wherein the vessel has a volume of at least 10,000 gallons.
 21. The system of claim 20, wherein the at least one sparge tube includes pores having pore sizes of 1 micron or less. 